Accessing Data on a Tape

[Amrit_1]

I have ftp'd some data on a tape say file A and B and in the above mentioned order i.e. file A first and then file B.

While accessing the tape is it possible to obtain the files in the reverse order i.e.
file B first and then the file A or is it something like a music tape wherein I can access only the first song and then need to fast forward to get the second song.

[Mark Grant · Accepted solution]

Amrit,

It depends how the data was put on the tape. If you used tar to copy files A and B as one archive then you can "simulate" the reverse order by un-tarring file B first. However, you can write data to tape anyhow you like and if you use the no-rewind device, it will be appended wherever the tape head happens to be. When you want to skip through to the next file you use "mt -f fsf X moves X files forward.

It is important to note that in this context "file" is more a session than an individual file so a tar archive of 1000 files, written as one operation would be considered one file.

Also bear in mind that most tapes need to be re-wound before taking them out- This means that if you wrote one "file", took the tape out and then wanted to write a second, you would need to use "mt" to move to the correct point one the tape first.